Rhenium-alumina catalyst and method of activating same with anhydrous treating agents

ABSTRACT

AN ACTIVATED RHENIUM-ALUMINA CATALYST IS PREPARED BY HEATING RHENIUM-CONTAINING ALUMINA AT 400-1500*F. IN A DRY AMBIENT AND TREATING IT WITH ANHYDROUS TREATING AGENTS, I.E. C.2, HCL, HBR, BR2 AND BR DERIVATIVES OF METHANE, AT 400-1500*F. THE ACTIVATED CATALYST FINDS UTILITY IN THE ISOMERIZATION OF PARAFFINS AND NAPHTHENES.

United States Patent 3,726,810 RHENIUM-ALUMINA CATALYST AND METHOD OFACTIVATIN G SAME WITH ANHYDROUS TREATING AGENTS John W. Myers,Bartlesville, Okla., assignor to Phillips Petroleum Company No Drawing.Filed Dec. 24, 1970, Ser. No. 101,419 Int. Cl. B013 11/78 US. Cl.252-441 9 Claims ABSTRACT OF THE DISCLOSURE An activated rhenium-aluminacatalyst is prepared by heating rhenium-containing alumina at 400-1500F. in a dry ambient and treating it with anhydrous treating agents, i.e.C1 HCl, HBr, Br and Cl and Br derivatives of methane, at 4001500 F. Theactivated catalyst finds utility in the isomerization of paraffins andnaphthenes.

This invention relates to a process for activating rhenium-containingalumina catalysts. In another aspect, this invention relates to anactivated rhenium-containing alumina catalyst composition. In yetanother aspect, this invention relates to an improved low temperatureprocess for the catalytic conversion of hydrocarbon feedstreams.

Modern motor fuels requirements have increasingly demanded high octaneratings. In fact, present day automotive fuels are almost comparable inoctane number to aviation gasoline of the past. As a consequence of thisrise in octane number, many new processes have been introduced inrefineries for the production of such high grade motor fuels andinclude, for example, alkylation, catalytic conversion of hydrocarbons,catalytic cracking and the like. In connection with such processes,particularly alkylation, a source of isoparaffin is necessary. Thus, ithas been necessary to provide new processes for the production ofisoparatfins, since natural sources of these materials 'are not nearlysufficient to supply present day needs. The most widely used method ofthe preparation of isoparatfins comprises isomerization of normalparalfins. Hydrocracklng of heavier hydrocarbons to produce lighterhydrocarbons is also practiced by the petroleum industry.

The catalytic conversion of hydrocarbons over platinum-on-alumina,promoted with noble metals has been practiced. Platinum catalysts, forexample, are highly selective toward the production of high octanearomatics and highly active for the several reactions that occur duringhydrocarbon conversion processing. However, platinum catalysts are alsovery expensive because of the high cost of platinum and will probablybecome even more expensive as a result of restricted availability of themetal. These economic factors have led the petroleum industry to seekless expensive substitutes for platinum and to investigate catalyticsystems using metal other than platinum.

An object of this invention is to provide a process for the formation ofactive rhenium-containing alumina catalysts which will provide suitablehydrocarbon conversion activities at relative low temperatures. Anotherobject of this invention is to provide a low-cost, long-life catalystfor the catalytic conversion of hydrocarbons. Still another object ofthis invention is to provide an improved catalytic process forhydrocarbon conversion, for example, the low temperature isomerizationof normal paraflins and naphthenes.

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Other aspects and objects of this invention will hereinafter appear.

In accordance with this invention, rhenium-containing alumina catalystsare rendered active by treating with anhydrous treating agents selectedfrom the group consisting of C1 HCl, Br HBr, mono-, di-, triandtetrachloromethane, and mono-, di-, triand tetrabromomethane. Theactivation process of the present invention is carried out by heatingthe rhenium-containing alumina catalyst in the presence of the abovetreating agents at a temperature of from about 400 to about 1500 F., fora period of at least 0.1 to hours in a dry ambient. The treating agentmay be used alone, or it may be carried in a stream of an essentiallyinert gas such as nitrogen, hydrogen, methane or ethane, wherein thehalogen comprises from 1 to 99 percent by volume of the activatingstream. The activating gas pressure (in the activation zone) is notcritical, but is usually about atmospheric or a convenient higherpressure.

In further accord with the invention, the rhenium-containing aluminumcatalyst activated by the above-described process can be used for thecatalytic conversion of hydrocarbon feedstreams. Paraffins ornaphthenes, for example, are isomerized by contact with the catalyst ofthe present invention at temperatures in the range of about 100 to 600F. The contact can be carried out at any convenient pressure Within therange of from 0 to 2000 p.s.i.g. and, preferably, in the presence ofsome free hydrogen. The catalyst activity can be maintained at a highlevel during use in the isomerization process by including small amountsof a halogen-containing compound in the feed.

The catalysts of the present invention can be prepared using anyconventional catalytic grade of alumina generally having a surface areaof at least 1 m. g. Eta-aluminas and gamma-aluminas prepared byprecipitation techniques are generally preferred. The alumina cancontain from about 0.1 to about 5, preferably from about 0.1 to about 3,weight percent rhenium. The rhenium is incorporated into the aluminausing any conventional catalyst preparation technique. Preferably, thealumina is impregnated by a suitable rhenium-containing solution, forexample, solutions of perrhenic acid or solutions of ammoniumperrhenates. In some instances, copromoting the rhenium-aluminacomposite with minor amounts of platinum group metals such as platinum,ruthenium, rhodium, palladium, iridium, and osmium can be beneficial.Following the impregnation, the rhenium-impregnated alumina can bewashed to remove any non-volatile materials, dried, then calcined, indry flowing air or a hydrogen stream, at 4'001500 F. for 0.1-100 hours.The calcination temperature is preferably at least 600 F.

Following this calcination, the composite is then, prefera'bly,subjected to a hydrogen treatment at elevated temperatures. Thus, thecomposite can be heated at 400- 1500 F., preferably 600-1500 F., for0.1-100 hours in dry flowing hydrogen. In some instances, the hydrogentreatment can take the place of the above-described calcination in air.

The above-described rhenium-containing composition which has beencalcined and subjected to an optional reduction in hydrogen treatment isthen contacted with the aforementioned anhydrous treating agents whileat a temperature of 400-1500 F., preferably 1050-1400" F., for a periodof at least 10 minutes and up to 100 hours or more, preferably 0.5-6hours. The treating gas pressure is not critical, but is usually aboutatmospheric or at some convenient higher pressure. Treatment of therhenium-contaiuing alumina composition using aqueous solutions, forexample aqueous solutions of hydrochloric or hydrobromic acid, does notproduce the active catalyst of the present invention.

For best results, it is important that, at the conclusion of thetreatment period, the temperature of the catalyst be reduced to atemperature in the operating range, for example 300 F., while still incontact with the treating gas. Once in the operating temperature range,the active catalyst can be flushed, if desired, with an inert gas suchas nitrogen, or it can be put directly in contact with the hydrocarbonfeedstream.

The catalyst is capable of long life, particularly when some hydrogen ispresent in the reaction zone. However, when the catalyst becomesdeactivated after long use, it can be regenerated by repeating thesequence of steps used in the initial catalyst preparation, namely, thecalcination in an oxygen-containing gas, the hydrogen treatment, ifdesired, and contacting the catalyst with a bromide and/ or chloridetreating agent.

Suitable feedstocks, for example paraflins or naphthenes, are isomerizedby contact with the catalyst of the present invention at temperatures inthe range of 100-600 F., preferably 100-500 F. The contact can becarried out at any convenient pressure within the range of 2000 p.s.i.g.Preferably, the isomerization is carried out in the presence of somefree hydrogen and the molar ratio of hydrogen to hydrocarbon willgenerally be in the range of 025-100. The feed rate for the process willgenerally be in the range of 5000 GHSV.

The activity of the catalyst can be maintained at a high level duringuse in the isomerization process by including 0.0011 weight percent of achlorine-containing compound in the feed. Such chlorine-containingcompounds can be chlorinated hydrocarbons such as carbon tetrachloride,chloroform, ethyl chloride, isopropyl chloride, and the like, andmixtures thereof. This is not a substitute for the activation process ofthe present invention, but aids in maintaining, over longer processperiods, the high level of catalyst activity produced by the presentinvention.

The isomerization process of the present invention is preferably carriedout continuously using any suitable contacting technique such as a fixedcatalyst bed or a fluidized catalyst bed. After leaving the reactionzone, the reaction effluent can be conventionally separated and thedesired products recovered. Hydrogen, if used, as well as anyunconverted feeds, can be recycled to the reaction zone.

This catalyst can be used according to the process of the presentinvention to isomerize paraffins and naphthenes. Paraffins such asstraight-chain paraffins having from about 4 to about 10 carbon atomsper molecule and naphthenes having from about 6 to about 10 carbon atomsper molecule are particularly suitable feedstocks. Some examples of suchfeeds are: n-butane, npentane, n-heptane, methylcyclopentane,dimethylcyclopentane, cyclohexane, butylcyclohexane, and the like, andmixtures thereof. Mixtures of paraflins and naphthenes such as areobtained from distillation of straight run or natural gasolines can beused.

The halogen-activated rhenium-alumina catalyst of the present inventioncan also be advantageously utilized in other hydrocarbon conversionssuch as hydrocracking, al'kylation, disproportionation, polymerization,hydrogentransfer, dealkylation, and other reactions requiring acidiccatalysts.

The following example is submitted for the purpose of illustration onlyand is not to be construed as a limitation upon the scope of theinvention.

EXAMPLE A 45.0 g. quantity of 14-20 mesh catalytic cta-alumina was dried2 hours in flowing air at 800 F. The alumina was then impregnated with aperrhenic acid solution. The solution was prepared by diluting 4.35 ml.of a perrhenic acid solution, which contained 0.052 g. Re/ml., to 31.5ml. with deionized water.

The above mixture was then dried at 230 F., then a 20 g. portion wascharged into a tubular fixed bed reactor and heated in a stream of dryhydrogen at 1200. F. for about 15 hours. The catalyst was then furthertreated for 1.5 hours in flowing hydrogen chloride gas at 1200 F. Thecatalyst was then cooled to 400 F. while still in the presence offlowing hydrogen chloride gas. It was then purged with a stream of drynitrogen gas.

While still in the fixed bed reactor, the above-activated catalyst wasthen contacted with a flow of n-butane at 153 F., 0 p.s.i.g., and agaseous hourly space velocity of 47. The essential conditions and theresults of this run are shown in Table I below. For purposes ofcomparison, a similarly prepared, but rhenium-free, alumina catalyst wasalso tested with the n-butane feed stream. The results of this test arealso shown in Table I below.

TAB LE I.ISOME RIZAT IO N O F n-B UTANE 1 Both catalysts activated inanhydrous H01 at 1,200 F.

Without chloride-activation, rhenium-alumina will give substantiallyzero conversion of butane at these experimental conditions.

The data in the table above show that halogen-treated Re/Al O catalystis very active and selective for the isomerization of n-butane. The dataalso show that the invention catalyst is more active than therhenium-free alumina catalyst under comparable conditions.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

What I claim is:

1. A process for the formation of an active rheniumcontaining aluminacatalyst, said catalyst consisting es sentially of alumina and from 0.01to 5 weight percent of rhenium, comprising heating saidrhenium-containing alumina at a temperature in the range of 400 to 1500F. in a dry ambient, and thereafter treating the heatedrhenium-containing alumina with at least one anhydrous treating agentselected from the group consisting of C1 HCl, HBr, Br and the Cl and Brderivatives of methane at a temperature of 400 to 1500" F., for at least10 minutes.

2. A process according to claim 1 wherein heating of saidrhenium-containing alumina is carried out in an anhydrous gas selectedfrom the group consisting of hydrogen and air for 0.1 to hours.

3. A process according to claim 2 wherein said heating is carried out inthe presence of hydrogen.

4. A process according to claim 1 wherein said anhydrous treating agentcontains chlorine.

5. A process according to claim 4 wherein said anhydrous treating agentis hydrogen chloride.

6. The process of claim 1 wherein said rhenium-containing alumina iscontacted with dry flowing hydrogen for 0.1 to 100 hours at atemperature of from about 400 to 1500 F.

7. A process according to claim 1 wherein said treating agent is presentin an amount of from 1 to 99' percent of a carrier gas which isessentially inert in the treating process.

5 8. The active rhenium-containing alumina catalyst prepared by theprocess of claim 1.

9. The active rhenium-containing alumina catalyst prepared by theprocess of claim 5.

References Cited UNITED STATES PATENTS 3,438,888 4/1969 Spurlock 208-1393,537,980 11/1970 Kluksdahl 208-139 3,557,022 1/1971 Rausch 260-683.68

6 FOREIGN PATENTS 1,164,687 9/1969 England 260683 D U.S. Cl. X.R.

